1. Field of Invention
The present invention relates to a stent for supplying oxygenated blood retrogradely to the myocardium via the coronary sinus. The stent directs blood from the left ventricle to the coronary sinus through a hole punctured through the wall of the coronary sinus and the wall of the left ventricle and by restricting the outflow of the coronary sinus directs that blood retrogradely.
2. Description of Related Technology
Retrograde perfusion using the coronary sinus has long been known for treating end-stage heart disease. Previous methods among others attempted to connect the aorta to the coronary sinus using a jugular vein or an internal mammary artery graft. These methods were invasive in nature and required open heart surgery.
U.S. Pat. No. 5,824,071, issued to Nelson et al. in 1998, discloses an apparatus and method for providing retrograde perfusion directly from the left ventricle to the coronary sinus. Nelson requires a pressure sensitive valve that prevents pressure build-up inside the coronary sinus from rising above 60 mm Hg. Nelson, however, does not teach how such a valve may be constructed, and it is unlikely that such a device may be introduced percutaneously.
In 2000, Patel et al. conducted experiments for percutaneous arterialization of the coronary sinus using a stent. See Patel et al., Percutaneous Transmyocardial Intracardiac Retroperfusion Shunts: Technical Feasibility in a Canine Model, JVIR 2000, 11:382-390. The stent employed by Patel et al., however, results in a significant shunt of oxygenating blood from the left ventricle to the right atrium (hereinafter xe2x80x9cleft-to-right shuntxe2x80x9d). Although Patel recommends using a T or a Y shaped device, technical problems associated with accurately delivering such a device in place render the invention difficult. These factors argue for a simpler device for providing retrograde perfusion to the heart via the coronary sinus.
It is an object of the present invention to provide a novel stent and a method for providing oxygenated blood retrogradely from the left ventricle to the heart tissue through the coronary sinus without a significant left-to-right shunt.
In a preferred embodiment, the present invention contemplates a stent having a leading end and a trailing end and having a passageway therethrough. After delivery, the body of the stent is expanded to fit securely within the coronary sinus. The leading end of the stent (hereinafter xe2x80x9cleading (LV) end) is positioned in the left ventricle, and the trailing end (hereinafter xe2x80x9ctrailing (RA) endxe2x80x9d) is positioned in the right atrium.
The stent has a reduced cross sectional diameter or a smaller passageway at the leading (LV) end and at the trailing (RA) end as compared to the remainder of the stent. The size of the passageway decreases or tapers toward the leading (LV) end and toward the trailing (RA) end. Accordingly, as blood flows into the small passageway of the leading (LV) end, the passageway broadens in diameter toward the midsection of the stent and decreases again toward the small passageway of the training (RA) end.
The smaller passageways at the leading (LV) end and at the trailing (RA) end of the stent operate to control the amount of blood flowing into and out of the coronary sinus. The size of the passageway at the leading (LV) end controls the amount of inflow into the coronary sinus.
The cover surrounding the stent at the trailing (RA) end directs blood flow through the passageway at the trailing (RA) end, and the size of the passageway at the trailing (RA) end controls the amount of outflow into the right atrium. They also control the retrograde flow of oxygenated blood to the myocardium, specifically that of the left ventricle. The stent forms a friction fit with the lumen of the coronary sinus.
The stent has a variable cross-sectional diameter to allow it to be compressed or expanded cross-sectionally. For example, the stent may be compressed cross sectionally to fit within a catheter. After percutaneous delivery into its desired position, the stent may self expand to form a friction fit within the coronary sinus. If a stent does not self expand, it may be expanded using a balloon as known in the art or other suitable mechanism. The present invention also contemplates a heat-dependent expansion stent made of nitinol. The stent is also made of a flexible material that allows bending without forming a kink.
The present invention also contemplates a percutaneous method for delivering and placing a stent of the present invention to allow blood flow from the left ventricle to the coronary sinus. A hole punctured percutaneously through the wall of the coronary sinus and the wall of the left ventricle creates a passageway for flow between the left ventricle and the coronary sinus. The hole is dilated using a balloon as known in the art. After the stent is delivered and positioned between the left ventricle and the right atrium, the sheath of the catheter is removed to expose the stent. Advantageously, the stent forms a friction fit with the interior wall of the coronary sinus as it expands. The trailing (RA) end protrudes through the coronary ostium and extends into the right atrium. The leading (LV) end protrudes through the hole in the wall of the coronary sinus and the wall of the left ventricle to extend into the left ventricle.
In the present invention, the smaller passageway and the cover of the trailing (RA) end restrict blood flow into the right atrium. Pressure inside the coronary sinus is increased, and the blood flows out through the open interstices of the stent retrogradely to perfuse the myocardium.
Some amount of blood flow into the right atrium through the coronary ostium, however, is necessary to control the pressure in the coronary sinus. The diameter of the passageway at the trailing (RA) end should be large enough to prevent the coronary sinus pressure from rising above a suitable pressure, preferably about 50 mm Hg, while reducing a significant amount of left-to-right shunt. It is believed that a suitable pressure limit is such as to avoid damage to the coronary sinus and the left ventricular venous system while effectively providing retrograde perfusion. An optional covering at the leading (LV) end of the stent will depend on stent design. It will help maintain the diameter of the hole in the left ventricular wall.
Thus, the present invention overcomes the difficulty in the prior art with an elegant and simple stent that retrogradely supplies oxygenated blood to the myocardium while decreasing the shunting of oxygenated blood from the left ventricle to the right atrium.